Resistor and method of making the same



Feb. 25, 1947. .1. A. VlCTOREEN 2,416,599

RESISTOR AND METHODDF MAKING THE SAME Filed Ndv. 5, 1943 INVEN TOR. JOHN A- V/CTOEE'E'N A TTOIPNEYS Patented Feb. 25, 1947 I John A. Victor-ecu, Cleveland, Ohio Application November 5, 1943, Serial No. 509,148

This invention relates to resistors and more particularly to a resistor having a relatively high resistance which resistance will remain substantially constant under adverse conditions.

Asis well known to those versed in the art, there are conditions in some electrical circuits where it is highly desirable to use very high ohmic resistance resistors. This is particularly true in so-called electrometer circuits wherethe currents to be measured are extremely low. Very often in these cases, the apparatus although theoretically possible of construction, will refuse to operate properly and consistently because the resistors used do not, durin use, maintain the same resistance. Sometimes such apparatus will work when first constructed but soon thereafter will cease to operate. As explained in my Patent No. 2,314,060 of March 16, 1943, this may be due to the gradual surface creepage of electrons across the envelope of the tube which thus may provide a resistance path of lower resistance which may actually be lower than the resistance in the input circuit. As explained in the above patent I discovered that this resistance path could be controlled, or the electron flow controlled, by placing in the path of electron flow a dam or obstruction which had high surface resistance to electron flow and which was held in place by a good wetting cement having a high volume resistance to electron flow. In this case the electrons could creep up to the dam, there they were stopped and could travel no further.

The present invention therefore utilizes the discovery of the before mentioned patent to provide for a specific improvement in the resistors. That is, a resistor having a resistance of 10 ohms at the start of operation may, because it is operating in a standard atmosphere, drop to a considerable fraction of this value due to the collection of moisture, etc., on its surface.

It is therefore an object of this invention to provide an improvement in resistors.

Another object of my invention is to provide a high resistance where the resistance value remains constant.

Another object of this invention is to provide a high value resistor which will have constant resistance value in spite of adverse atmospheric conditions.

Another object of my invention is to provide an improved method of manufacture of a resistor having high resistance values. v

Still another object of my invention is to provide a resistor which is of delicate construction 8 Claims. (CL 201-) and yet is rugged and not liable to change its value because of handling or rough usage.

Still other objects of the invention and the invention itself will become moreapparent from the following description of an embodiment thereof which description is illustrated by the accompanying drawing.

The figure of the drawing is an enlarged detailed view of a resistor embodying the precepts of my invention. I

Referring to the drawing, there is illustrated at I a glass rod. 'This rod. is provided with a 'coating of conducting material having a resistance which may be dependent upon the thickness thereof or on the type of material. The ends of the rod'have sealed therein wires. and 5. At I this point it may be stated that the rod does not necessarily have to be of glass but can be any suitable material having a high resistance or insulation quality, and that the coating may be a colloidal conductor such as colloidal graphite or the like. Although the wires are stated as being seaiedin the ends of the rods they may be secured thereto by metal caps pressed over the ends if desired, the description being illustrative of a, preferred form.-

Preferably the ends of the rod in a short zone 3 are provided with a heavy conductive coating which connects the outer body of the rodand the coating 2 to the wires 4 and 5.

The unit comprising the rod with its coating and wires is sealed in a tube or envelope '6, the wires extending through presses I in the opposite ends of the envelope. Here again it is not necessary that a tube with the wires extending, out of opposite ends be used for the envelope; but the envelope may be of anysize or shape with the wires coming out of the same end or side. In the case illustrated, however, it forms a convenient means for subsequent installation of the resistor besides reducing the capacity between the lead wires 4 and 5.

At "this point it should also be noted that the wire 5 is provided with an S shaped bend which permits freedom of expansion of the various elements relative to each other without disturb- At one end of the'tube and around one of the i presses l and the wire 5, is disposed a ,thimble or bead 8 which is secured to the surface of the tube by a cement 9, which wets the surface of the tube and the bead, and holds the bead securely in place. 7

The bead 8 may be of amber, polystyrene or the like substance, characterized by having extremely high surface resistance to electron flow. The cement 9 may be any suitable cement that is capable of wetting the surface of the envelope and the bead, and having high volume resistance to electron flow. One such cement is De Khotinsky cement such as is described in the 21st edition of the Handbook of Chemistry and Physics by Charles D. Hodgman.

When a resistor is constructed as described, electrons may creep across the envelope but when they reach the bead 8 they are definitely stopped. Therefore, since they cannot reach the other lead, because the bead or dam completely closes the path to the lead, they do not complete the circuit and the resistance is maintained constant and that of the resistance of the film 2.

Another feature of this invention resides in the method of manufacture of the device.

In constructing the device I first take a rod i, heat the ends and press the wires ii and into the molten ends after which they are allowed to cool sealing the wire securely therein. Next I apply a heavy coating of conductive material, which may be a colloidal conducting material such as colloidal graphite,.by painting it on the ends of the rod and onto the wires where they join the rod.

The assembly is then dipped in asolution of a colloidal conducting material suspended in a colloidal insulating medium such as gelatine and dried in an oven or the air at approximately 50 centigrade. It'is preferable at this time that the surrounding air be dry so that all moisture is excluded.

Next the assembly is inserted in a tube and the ends sealed as at l. Simultaneously the tube may be evacuated or filled with inert gas.

Finally the resistor is then baked at a predetermined temperature for a sufficient time until the resistance becomes stabilized at the desired value. Then the bead 8 is cemented in place around the lead 8..

Another feature of my discovery is that the resistance value of the device is determined by the temperature at which it is baked and that during the baking process the resistance value changes during the early period and gradually becomes stabilized as the baking progresses until it finally reaches a point where it does not change with further baking. The resistor is therefore baked until this period is reached after which it, is ready for the application of the bead. Also it should be noted that the resistance can be determined by the temperature at which it is baked, for instance, if it is baked at 120 C. it ultimately reaches a different value than if baked at 122. Therefore, resistors may be similarly constructed and the resistance value of the resistors, which might otherwise be the same, caused to be differcut by reason of, the different baking temperature.

With a resistor constructed as described extremely high values may be produced. In use the resistance remains stable and is not changed due to atmospheric effects, such as moisture or the like. l

may be made therefrom without departing from the spirit or scope of the invention.

I claim:

1. The method of manufacturing resistors which have a rod with a conductive coating and leads extending therefrom and disposed in an envelope which comprises ealing the leads in the rod, applying a heavy coating of conductive material to the ends of the rods adjacent the lead, dipping the rods to apply a coating of conductive material, drying the rods, sealing them in the envelope and baking the assembly until the resistance reaches the desired value;

2. The method of manufacturing resistors which have a rod with a conductive coating and leads extending therefrom and disposed in an envelope which comprises sealing the leads in the rod, applying a heavy coating of conductive material to the ends of the rods adjacent the lead, dipping the rods to apply a coating of conductive material, drying the rods, sealing them in the envelope and baking at a predetermined temperature until the resistance value becomes stabilized.

3. A resistor comprising a rod like member of insulating material, a conductive coating of high resistance material deposited on the surface of said rod. connections for the ends of said rods electrically connected to said conductive coating, an envelope for enclosing said road, said conductors extending in sealed relation through said envelope, the interior of said envelope being under vacuum and means on the exterior of the envelope to increase the surface resistance between said leads comprising a member formed of a material having high surface resistance to electron flow secured in place on the envelope b a material having high volume resistance to electron flow.

4; A resistor comprising a rod like member of insulating material, a conductive coating of high resistance material deposited on the surface of said rod, connections for the ends of said rods electrically connected to said conductive coating,

r' an envelope for enclosing said rod, said conductors extending in sealed relation through said envelope, the interior of said envelope being under vacuum and means on the exterior of the envelope to increase the surface resistance between said leads comprising a member of amber, polystyrene or the like held in place on the envelope by a cement having properties of high volume resistance to electron flow said member isolating one connection from the other.

5. A resistor comprising a rod like member of insulating material, a thin film of high resistance coating on said rod, connectors for said rod, an envelope for inclosing said rod, said connectors extending through said envelope in sealed relation thereto and means to prevent surface creepage of electrons between said connectors com- I prising a dam of high surface resistance mate- Having thus described my invention I am rial secured in place on said envelope by a cement having high volume resistivity.

6. A resistor comprising a rod like member of insulating material, a thin film of high resistance coating on said rod, connectors for said rod, an envelope for inclosing said rod, said connectors extending through said envelope in sealed relation thereto and means to prevent surface creepage of electrons between said connectors comprising an amber dam having high surface resistance to electron flow secured in place on the envelope by De Khotinsky cement.

7. A resistor comprising a rod like member of envelope for inclosing said rod, said connectors extending through said envelope in sealed relation thereto and means to prevent surface creepage of electrons between said connectors comprising a ring'of polystyrene or the like secured in place by a cement having high volume resistivity.

8. A resistor comprising a glass rod, conductors sealed in the ends of said rod, a conductive coating for coating the ends of the rod and electrically connected to said conductors, a resistance coating disposed on the body of said rod intermediate said end coatings and electrically connected thereto, an envelope for enclosing said rod and excluding the atmosphere therefrom, said conductors extending in sealed relation through said envelope at least one of said conductors formed to permit expansion and contraction interiorly of the envelope, and means on the exterior of said envelope to prevent surface creepage of electrons across the envelope comprising a material 0d high surface resistivity forming a complete electrical obstruction to isolate said conductors secured in place on the envelope by a. material of high volume resistivity.

JOHN A. VICTOREEN.

REFERENCES CITED The following references are of record in the file of this patent:

I UNITED STATES PATENTS Number Name Date 1,682,457 ZWorykin Aug. 28, 1928 1,388,373 Richtmyer Aug. 23, 1921 1,751,587 Loewe Mar. 25, 1930 2,215,587 Kerschbaum Sept. 24, 1940 2,297,780 Pugh, Sr. Oct. 6, 1912 1,715,879 Wells June 4, 1929 1,694,167 Dubilier Dec. 4 1928 1,596,852 Morrison Sept. 2, 1924 1,635,184 Jones July 12, 1927 1,473,107 Kohn Nov. 6, 1923 1,832,419 Pender Nov. 17, 1931 

